"We, the family, are supporting each other here at Maria's side and we take great comfort from the remarkable medical care she has been receiving," her sister Isabel said in a statement released by the Russian-owned team.

F1 family: The De Villotas 4 photos

F1 family: The De Villotas4 photos

Maria de Villota: 1980-2013 – Former Formula One test driver Maria de Villota passed away aged 33. "It is presumed to be death by natural causes," a National Police spokeswoman said Friday.

Hide Caption

1 of 4

F1 family: The De Villotas4 photos

Joining the men – Spain's De Villota was the first female driver to join a Formula One team in 20 years.

Hide Caption

2 of 4

F1 family: The De Villotas4 photos

F1 family – Maria's father Emilio de Villota is a pilot and former racing driver. He runs his own team in the Spanish Formula Three championship.

Hide Caption

3 of 4

F1 family: The De Villotas4 photos

Like father, like daughter? – He entered 15 Formula One races between 1976 and 1982, but qualified to start only two of them with a best finish of 13th.

Just Watched

Female F1 driver De Villota in profile

"We remain positive and this is due, in no small part, to the overwhelming expression of love and support for Maria from every corner of the world.

"We would also wish to thank everyone at the Marussia F1 Team for all the care and attention they have shown us over the past few days."

Tuesday was the first time De Villota had been behind the wheel of Marussia's MR01 car, although she did conduct a test for the Renault team last year.

"Maria remains in a critical but stable condition," added De Villota's sister.

"While there is no further news than that at present, we have at least been able to take encouragement from the fact that Maria has remained stable throughout since the accident, particularly during the first night following such a lengthy surgical procedure as she experienced."

The De Villota family has a rich motorsport heritage. Maria's father Emilio was a Formula One driver between 1976 and 1982.

The only other female driver currently involved in the elite division of motorsport is Susie Wolff, who is a development driver with Williams.